1. Field of The Invention
The subject invention relates to the recording of video images and sound, and more particularly, to the recording of these video images and sound for the purpose of editing the recording.
2. Description of The Related Art
Video recording for the recording of image and sound of scenes is generally known today. A camera converts image and sound into electric signals which are stored on a carrier such as a magnetic tape; a playback apparatus reads these signals from the carrier and generates a signal for application to a reproducing apparatus, such as a monitor or a television set, in order to be reproduced.
Conventional practice was to record these electric video signals in analog form. Nowadays digital recording is also known, for which compression techniques, such as DVC, can be used. In both cases, the recording may be regarded as a sequence or series of recorded images with associated sound, these images having been provided with a unique identification number.
In the field of image recording and reproduction, there is a need to be able to arrange the recorded images in a sequence which deviates from the recorded sequence. This is the case, for example, with an amateur film-maker who wishes to make a holiday film, but it also applies to a professional film-maker who can or wishes to use only a part of his/her recordings. Prior to the actual pasting, the user should view and judge the recorded sequence and decide which parts of this sequence he/she wishes to use for recording on a target carrier and in what order; this process will be referred hereinafter as "editing".
Conventional editing is effected by simply playing the carrier with the recordings on a playback apparatus, viewing the reproduced images, and taking notes. Images are pasted in a conventional manner by playing back a carrier with recordings by means of a playback apparatus and by applying the electric signals generated by this playback apparatus to a recording apparatus to record them on another carrier. To paste a recording at a desired location, the user positions the recording head of the recording apparatus at the desired location with respect to the target carrier, positions the playback head of the playback apparatus at the beginning of the desired recording on the source carrier, and subsequently starts the playback apparatus and the recording apparatus at the same time. However, this is a rather intricate, time-consuming and inaccurate procedure.
Therefore, in order to achieve a greater ease of use, computer programs have been developed for the editing of recordings. The recordings are then read into a computer memory. Subsequently, the user views the images read into the computer memory on a monitor or television set for the purpose of editing and gives edit commands to the computer in accordance with his/her edit decisions. In response to the edit commands entered by the user, the computer then reads the images from the memory in the sequence determined by the user, the image signals being available on a signal output of this computer in order to be recorded on the target carrier.
It will be evident that these tasks can be performed not only by a dedicated computer, but also by a suitably programmed standard computer such as a PC. Hereinafter, such a computer will also be referred to as an editing computer.
The use of such a computer presents various problems.
First of all, the required amount of storage capacity is comparatively large. For example, the storage of video recordings having a length of 1 hour requires approximately 11 GB when the digital signals have been compressed in accordance with the DVC format. It is to be noted that hereinafter, it is assumed that the recordings have been compressed in accordance with the DVC format, but it will be evident that the invention is not limited thereto. The use of other compression techniques is also conceivable. Alternatively, the recordings may have been recorded in analog form, but in order to save storage capacity, it is preferred to use a compression technique, such as DVC, for reading into the computer memory.
Secondly, it takes much time to read these video recordings into the memory. Normally, the playback apparatus being used can play the source carrier only at the "normal" speed, which implies that the read-in of said video recordings then takes 1 hour. It is true that some playback equipment is capable of playing at two or even four times the "normal" speed, but this equipment is fairly expensive.
Thirdly, a comparatively high bit-rate is required for editing the images read into the memory. When the digital signals have been compressed in accordance with the DVC format, the bit-rate during read-out from the memory is approximately 25 Mbit/s. This also holds for the read-in of the recordings.